Ultrasound characteristics of subdermally implanted Implanon contraceptive rods

This study was designed to define sonographic characteristics and the optimal sonographic technique for localization of the single rod Implanon system. Diagnostic ultrasonography was performed in eight women who had the Implanon rod implanted in the medial aspect of the upper arm. All implants were scanned in the longitudinal and transverse direction using 3.5 MHz, 5 MHz, and 7.5 MHz linear array transducers. Scanning was performed both directly against the skin and with 2 and 4 cm Kiteco ultrasound stand-off pads. Each image obtained was evaluated for detectability of the Implanon rod and the grade of acoustic shadowing produced by the Implanon rod by two independent observers. Discrepancies in evaluation were adjudicated by a third observer. The Implanon rod implant was not directly identified using the transducer and standoff pad combinations. Implanon rods were indirectly identified as a result of the posterior acoustic shadow cast by the Implanon. Best demonstration was achieved with the 5 or 7.5 MHz transducer and a 2 cm stand-off pad in the transverse direction. Appropriate ultrasonographic technique and familiarity with posterior acoustic shadowing patterns generated by the implant provide a noninvasive method for localization of nonpalpable, single rod implants prior to removal.